It is frequently desirable to remove a portion or all of the water or other liquid component of a substance in order to stabilize materials associated with the liquid. Examples of such processes are lyophilization and spray drying.
The process of lyophilization meets many of the desired goals. However, it requires that the sample be first frozen and then lyophilized in a high vacuum. See U.S. Pat. Nos. 3,721,725 and 3,932,943. Because of these several steps, the process requires considerable time. Also, the resultant product suffers from being inhomogeneous due to the uneven freezing and the resultant inhomogeneity of dissolved materials recovered from a frozen state. In addition, the product of lyophilization is characteristically very hygroscopic.
The process of spray drying requires the evaporation of water from droplets of spray by use of high temperature gases. The result is that heat sensitive elements in the treated material may become inactivated, denatured or hydrolized. The powder resulting from spray drying, however, is normally much less hydroscopic than the product of lyophilization.